Grinding fixture for spade drill and the like



Nov. 27, 1962 M. BENJAMIN ET AL 3,065,580

GRINDING FIXTURE FOR SPADE DRILL AND THE LIKE Original Filed May 20, 1959 3 Sheets-Sheet l INVEN ORS MILTON L. BENJAMI ELMER LJ. SYRENE AT TORNEYS Nov. 27, 1962 M. L. BENJAMIN ET AL 3,065,580

GRINDING FIXTURE FOR SPADE DRILL AND THE LIKE Original Filed May 20, 1959 5 Sheets-Sheet 2 INVENTORS MILTON L. BENJAMIN ELMER L. J. SYRENE A TORNEYS Nov. 27, 1962 M. L. BENJAMIN ET AL 3,065,580

GRINDING FIXTURE FOR SPADE DRILL AND THE LIKE Original Filed May 20, 1959 3 Sheets-Sheet 3 INVENTORS BQNJAMIN T L. 'EEJXER L.J. mm:

- 0m 7$a F'E W ATTORNEYS 1 Claim. (Cl. 51-220) This application is a division of our application Serial No. 814,522, filed May 20, 1959.

The present invention relates generally as indicated to a spade drill and grinding fixture therefor and more particularly to certain improvements in the spade drill blade, in the blade-holder combination, and in the blade sharpening or regrinding fixture.

In general, it is well-known to provide so-called spade drills in which a blade is clamped in a holder and in which the holder is provided with passages for flow of coolant toward the cutting edges of the blade for cooling the blade and for flushing out the chips from the hole being drilled through flutes or flats formed on the opposite sides of the holder. It is also known in the art to provide various types of blade grinding or sharpening fixtures but, to my knowledge, all of such fixtures are designed to locate the blade from faces other than those used when the blade is mounted in the holder, thereby leading to inaccuracy in mounting and poor quality drilling action.

Accordingly, it is a main object of this invention to provide a novel form of spade drill blade, holder, and grinding fixture which results in much increased blade life, increased production (for example, the feed rate increased from 50% to 100% or more), elimination of binding or chattering in use, and economy and ease of duplication of factory-grade sharpness and accuracy in user regnound blades.

It is another object of this invention to provide a spade drill in which the blade is securely and accurately mounted in the holder and in which the holder and the blade define therebetween thin and wide fan-shaped coolant passages for directing uniform thin and wide film-like streams of coolant toward the cutting edges of the blade to make most efiicient use of the heat extracting properties of the coolant.

It is another object of this invention to provide a blade regrinding or sharpening fixture which is of very simple unitary construction and in which the blade to be reground or sharpened is accurately located in the fixture from the same surfaces as are used to locate the blade when mounted in the holder.

' Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claim, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of a fewof the various ways in which the principle of the invention may be employed.

In said annexed drawings:

FIGS. 1, 2, and 3, are, respectively, top plan, side elevation, and end elevation views of a spade drill embodying the present invention;

FIG. 4 is a cross-section view of the end of the holder (without the blade), such section having been taken substantially along the line 44, FIG. 2, on somewhat enlarged scale; 7

FIG. is a view similar to FIG, 4 except showing how 3,065,580 Patented Nov. 27, 1962 ice the blade is accurately and detachably mounted in the slotted end of the holder;

FIGS. 6 and 7 are top plan and end elevation views, respectively, of a modified form of spade drill blade having longitudinally extending and parallel locating ribs along opposite sides thereof by which the blade is adapted to be supported in coaxial relation to the holder therefor;

FIGS. 8, 9 and 10 are respectively top plan, end elevation, and side elevation views showing a preferred form of spade drill blade embodying the improvements herein;

FIGS. 11 to 15 show the novel grinding or sharpening fixture herein in several different positions for performing the several grinding or sharpening operations on a blade mounted thereon; and

FIGS. 16 and 17 are top plan and end elevation views of a cylindrical grinding fixture.

The Spade Drill (a) The h0lder.-As best shown in FIGS. 1 to 5, the holder 1 comprises an elongated cylindrical body 2, and a shank 3 by which the holder is adapted to be held in a machine spindle, lathe turret or the like.

The end of the body 2 is formed with a slot extending diametrically thereacross formed with parallel sides 4 that are equidistant from the axis of the holder and with a fiat bottom 5 which lies in a plane perpendicular to the axis of the holder. The slotted end of the holder is also formed with parallel flats 6 which are perpendicular to the opposite sides 4 and bottom 5 of the slot.'

As shown, the holder 1 is formed with a centralaxially extending passage 7 which intersects the bottom 5 of the slot and terminates in radially extending passages 8 and 9 in the body 2 and in the shank 3 through which coolant is adapted to be supplied in well-known manner for flow through the passage 7 toward the slotted end of the holder. In the case of some tapered and all straight shank holders, such passage 7 may extend through the end of the shank,

The opposite sides '4 of the slot are formed with relatively thin and Wide fan-shaped channels 10 which, as best shown in FIG. 4, intersect the central coolant passage 7 so that in use, with a blade 11 mounted in place, the coolant will emerge from such fiat and wide channels 10 in the form of wide film-like streams whereby coolant will flow toward the cutting edges of the blade 11 in the manner indicated by the arrows in FIG. 1. By way of example, in a holder 1 for a 1%" wide blade 11 the depth of the channels 10 may be about and the width at the mouths thereof may be about /2".

The blade 11 referred to has a pair of cutting edges 12 at its pointed cutting end and is recessed at its other end to provide relieved locating faces 14 and 15 that respectively abut and embrace the flat bottom 5 of the holder slot and the parallel flats 6. The blade 11 is of thickness to have a close fit between the parallel sides 4 of the holder slot. The blade 11 isheld in place as by means of the screw 16, which, when tightened, draws together the spaced portions of the slotted portion of the holder 1 into firm frictional engagement with the opposite faces of the blade. It is to be noted that the blade 11 is formed with a hole 17 transversely therethrough which is of diameter substantially larger than the body of the screw 16 so that the blade 11 will be accurately located in a coaxial position in the holder 1 through the aforesaid locatprogressively increasing depth from the slotted end toward the shank end whereby to prevent congestion of chips therein. Preferably, the front ends of the fiutes 19 are relieved as at 20 to provide added space for easy entry and smooth flow of chips into the flutes 19.

In any case, it is to be observed that the wide and shallow fan-shaped channels that are formed in the holder 1 define with the opposite plane faces of the blade 11, a pair of wide and thin passages for emergence of corresponding streams of coolant from the central passage 7 directed toward the respective cutting edges 12 of the blade 11 to thus efiect eflicient cooling action.

(b) The spade drill blade.-The blade 11, as best shown in FIGS. 8, 9, and 10, essentially comprises a flat body of suitable material which is formed with a pointed cutting end including the aforesaid cutting edges 12. Also, as aforesaid, the blade 11 is formed with a hole 17 transversely therethrough and with the locating faces 14 and 15 at the other end by which the blade may be securely and accurately mounted in a holder, such as the holder 1 previously referred to.

Preferably, the cutting edges 12 of the blade 11 will be formed with top rake grooves and with primary and setondary relief surfaces 26 and 27. Also, the cutting and will beformed with chip breaker grooves 28 if these are found desirable or necessary.

The sides of the blade 11 are preferably cylindrical ground to provide cylindrical guide surfaces 29 which engage the side of the hole being drilled, such faces 29 being relieved as at 30.

The side edges 29 of the blade 11' are preferably formed with top relief 31 so that the outermost corners of the cutting edges 12 will be circumferentially advanced with respect to the cylinder-ground side edges 29, this having} been found to be very important in preventing heeling action and in eliminating binding and chattering of the. drill and in eliminating cutting action by such side edges 29.

A characterizing feature of the top rake 25 is that it is ground as with a plain cylindrical wheel that has a rounded corner whereby there is greater strength at each cutting edge 12 as compared with known grinding techniques in which radius wheels are employed to make the top rake grooves of concavely curved form. Also, the present blade 11 employs a straight. cut in the forming of the top rake grooves 25 whereas, the present known technique involves using a 3 offset between the grinding wheel and the cutting edge when forming the top rake. The. top rake grooves 25 herein are inclined toward the chisel edge 32 to reduce the. web thickness to a minimum and thus enable easy penetration of the blade. 11 into the. work with light axial thrust. loads. Because the radius of the rounded corner of the Wheel is not critical herein, less frequent. wheel dressing is required than in cases i where the top rake grooves are of concavely curved form of prescribed radius.

Added strength may be imparted to the. cutting edges 12. by leaving a slight. flat (.010 for example) between the cutting edges 12 and the leading edges of the top rake grooves 25. i

The blade 35 shown in FIGS. 6 and 7 essentially the same as that shown in FIGS. 1 to 5, and 8 to 10, except that said FIGS. 6 and 7 blade is formed with longitudinally extending ribs 36 of which the inside faces 37 are adapted to engage the parallel flats 6 formed at the slotted end of the. holder 1 and thus added rigidity is provided for holding the blade 35 in coaxial alignment with the holder 1.

The Cylindrical, Grinding Fixture This fixture 38' as Shown in FIGS. 16 and 17 generally resembles the holder 1 in that it is in the form of a bar provided with a flat face 4 against which the blade is clamped as by a screw 16, and with fiat faces 5 and 6 engaging the faces 14 and 15 of the blade, the point 4 32 of the blade being engaged by an axially adjustable brass screw 39 or the like to hold the faces 14 and 15 in firm abutting engagement. With a blade thus held in the fixture it may be used in any conventional cylindrical grinder to grind the surfaces 29 along the opposite side edges of the blade 11. This fixture may also be formed with flat sides 40 on which it is adapted to be set to grind the top relief 31 on each side of the blade 11, the surfaces 31 and 40 preferably being parallel as shown.

The Blade Grinding or Sharpening Fixture (FIGS. 11 to 15 The fixture 41 basically comprises a solid block of metal which has front and rear plane faces 42 and 43, parallel and plane end faces 45 and 46 and top and bottom plane faces 47 and 48. g

The top face 47 of the fixture 41 is formed with a diagonally disposed groove 49 adjacent one end or the other of which a block 50 is secured by the screw 51, said block 50 being of rectangular form so as to provide side and end faces that are perpendicular to each other and to top face 47. Also mounted in said groove 49 is the longitudinally adjustable bracket 52 which has an upstanding rectangular block portion 53 which likewise presents side and end faces that are perpendicular to each other and to the top face 47. Said bracket 52 is formed with a longitudinally extending slot 54 and is held in longitudinally adjusted position as by means of the screw '56- which has threaded engagement with the fixture 41. Another portion 53- may be provided at the other end of bracket 52 to avoid necessity of reversal as hereinafter explained.

The top face 47 of the fixture 41 is also formed with two pairs of threaded holes 57 and 58 disposed on opposite sides of the groove 49 to accommodate a screw post 59 for a clamping member 60, said clamping member 60 having a screw 61 threadedly engaged therewith to bear on the recessed top face 47 of the fixture. Thus by manipulating the screw 61 and nut 62 the free end 63 of the clamping member 60 is brought to bear down on the blade 11. When the blade 11 is to be held on the upper left end of the fixture 41, as shown in FIG. 11, the clamping member 60 will be mounted in either threaded hole 57 according to the size of the blade 11.

(a) Grinding of secondary relief 27.To perform this operation on a blade 11, the latter is placed on the top face 47 of the fixture as shown in FIG. 11, the screw 56 for holding the adjustable bracket or slide '52 having been loosened so that the side and end of the block portion 53 thereof and the side and end of block 50 will engage the locating faces 14 and 15 of the blade 11 to be ground. With the slide 52 thus adjusted, the screw 56 is tightened and the. screw 61 and nut 62 are manipulated to cause the clamping member 60' to clamp the blade 11 on the top face 47 of the fixture.

The blade 11 is thus supported in an inclined position with its edge 12 (see FIG. 12) disposed so that a vertical plane passing therethrough intersects a plane normal to. the top face of the blade 11 at the required secondary relief angle of 14 for example. Such vertical plane through edge 12 will also be parallel to front face 42 and perpendicular to bottom face 48 whereby the secondary relief 27 may easily be ground by placing the bottom face 48 on a horizontal table T of a grinder and the front face 42 against a guide G on the table while, say, the fiat vertical side of a grinding wheel W parallel to the guide, is moved against the end of the blade 11.

The groove 49 and front face 42 of the fixture are angularly related to provide the conventional point angle as used on spade drills, but if other point angles are desired, these may be easily achieved by performing the well-known sine bar calculations because the front face 42 of the fixture 41 is exactly 5" long. Thus, the blade 11 may be ground to best suit the materials of work pieces or foispot facing, counterboring or other operations.

(b) Grinding of primary relief 2-6.The primary relief 26 for the cutting edge 12, usually about 7, for example, is obtained by turning the fixture 41 so that it rests on its rear face 43 on a horizontal support. In that case, the blade 11 will be tilted back, as shown in FIG. 13, to an angle of 7 so that relative horizontal movement of the wheel W and fixture will grind the horizontally disposed primary relief surface 26 which of course is inclined 7 with respect to the top surface of the blade 11.

(c) Grinding of side relief 30.-The side relief 30' for the cylindrical grind 29 is obtained by placing the fixture 41 with its end face 46 resting on a horizontal support as in FIG. 14 whereby the blade 11 is tilted so that a horizontal plane passing through exposed side of the blade will be in a horizontal plane and at the required side relief angle with respect to a plane normal to the top face of the blade. Thus a wheel W moved horizontally as in FIG. 14 will grind the side relief 30.

The foregoing operations a, b, and 0 may then be repeated for the other cutting edge 12 and the other side of the blade by loosening the clamping member 60 and turning the blade 11 upside down.

(d) Grinding of top rake 25.-To perform this operation the block 50 is mounted adjacent the other end of the fixture 41 as shown in FIG. 15, and the adjustable bracket 52 is turned end for end and adjusted so that it and the block 50 will engage the locating surfaces 14 and 15 of the blade 11 and, of course, the screw post 59 of the clamping member 60 will be mounted in one or the other of the threaded holes 58. With the blade 11 mounted as in FIG. 15, with its bottom face 48 resting on the horizontal table or surface plate or the like, of the grinder, all that it is necessary to do is to move the fixture 41 or the wheel W with its horizontal axis moving in a horizontal plane and its peripheral edge E radiused but without requiring precision forming of the radius on the wheel since the curved portion of the top rake grooves 25 will function as a chip curler without providing any precise radius on the edge of the wheel W. In this case the blade is properly tilted to provide, not only the necessary top rake angle, but also a web thinning effect at the point 32. Because the portion of the top rake groove 25 adjacent to the cutting edge 12 is a plane surface rather than the conventional concave surface, the cutting edge 12 is greatly strengthened to the extent that double or triple feeds may be employed. For instance, the spade drill herein may be fed at the rate of .040" per revolution, as compared with the .015 to .020 per revolution when known grinding techniques are used.

(e) Grinding of the top cylindrical grind relief 31. While the fixture 41 herein does not make special provision for grinding the top relief 31 of the cylindrical grind 29, this can, of course, be done with the cylindrical grind fixture previously mentioned or other conventional holders wherein the grinding wheel axis and side 29 of the blade 11 are parallel.

SUMMARY From the foregoing, it can be seen that the present invention provides a new form of spade drill comprising the holder 1 and blade 11, a new spade drill blade 11, and a new grinding fixture 41 for facilitating the accurate and easy grinding or sharpening of spade drill blades 11. As aforesaid, the effective coolant supply through the thin and wide fan shaped channels to the cutting edges 12 of the blade under the chips curled by curling grooves 25, and the novel top rake grooves 25 provide for greatly enhanced life of the blade 11, together with quicker, more accurate drilling of smooth and round holes with greater rates of feed than currently are possible. Also, the top relief 31 of the side cylindrical grind 29 of the blade 11 positions the outer corners of the cutting edges 12 circumferentially ahead of the blade guide surfaces 29 so as to eliminate heeling action and to eliminate binding and cutting action by the sides of the blade.

In conclusion, several features of this invention con tribute to greater accuracy in the drilling of holes in workpieces, much increased blade life, and much greater feeds (50% to 100% or more) at reduced horsepower.

It is to be understood that the blade guide surfaces 29 may be cylindrical-ground with conventional backtaper, for example, .001 inch/inch of length of the sides of the blade 11.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in the following claim, or the equivalent of such, be employed.

We therefore particularly point out and distinctly claim as our invention:

A grinding fixture for a workpiece comprising a unitary substantially rectangular block having front and rear plane faces, parallel plane end faces, and top and bottom plane faces, and top face being formed with a diagonally extending groove, slidable clamping means mounted in said groove adapted to clamp such workpiece thereto in overhanging relation to said front plane face and one of said end faces and also adapted to clamp said workpiece in overhanging relation to said rear plane surface and the other end face when said clamping means is moved from one position to another position, said clamping means being provided with upstanding projections adapted to engage vertical surfaces on said workpiece, said bottom plane face being disposed at a predetermined angle with respect to said top plane face, said predetermined angle between said top and bottom plane faces being relatively small, and less than said rear plane face intersecting said top and bottom plane faces and being disposed at a predetermined angle with respect to said top plane face, said predetermined angle between said top and rear plane faces being slightly larger than 90, whereby two angularly related faces of such workpiece can be ground respectively by the side and peripheral face of a grinding wheel having a horizontal axis of rotation by horizontally supporting said fixture, with such workpiece clamped thereto, on said bottom and one of said rear plane faces, respectively, with said clamp in said one position and whereby two other angularly related faces of such workpiece can be ground respectively by the side and peripheral faces of said grinding wheel by horizontally supporting said fixture with such workpiece clamped thereto on said bottom and the other of said rear plane faces with said clamp in said another position.

References Cited in the file of this patent UNITED STATES PATENTS 1,694,560 Parish Dec. 11, 1928 2,385,902 Wilson Oct. 2, 1945 2,409,936 Hunt Oct. 22, 1946 2,595,950 Keebler May 6, 1952 2,626,491 Penkoif et al. Jan. 27, 1953 2,912,801 Sherman Nov. 17, 1959 

